Generally, the widely-used peripheral input device of a computer system includes for example a mouse device, a keyboard device, a trackball device, or the like. Via the keyboard device, characters or symbols can be directly inputted into the computer system. As a consequence, most users and most manufacturers of input devices pay much attention to the development of the keyboard devices.
Hereinafter, the structure and function of a conventional keyboard device will be illustrated with reference to FIGS. 1 and 2. FIG. 1 is a schematic cross-sectional view illustrating a mechanical key structure of a conventional keyboard device. FIG. 2 is a schematic cross-sectional view illustrating the mechanical switch of the conventional keyboard device when a keycap of the mechanical key structure is depressed. The keyboard device 1 comprises plural mechanical key structures 12 and a circuit board 11. For succinctness, only one mechanical key structure 12 is shown in the drawings. Each mechanical key structure 12 comprises a keycap 121 and a mechanical switch 124. The mechanical switch 124 comprises a casing 1241, a push element 1242, a linkage element 1243, a first spring strip 1244, a second spring strip 1245 and an elastic element 1246. The linkage element 1243, the elastic element 1246, at least a part of the push element 1242, at least a part of the first spring strip 1244 and at least a part of the second spring strip 1245 are accommodated within the casing 1241.
The casing 1241 comprises a pedestal 12411 and an upper cover 12412. The pedestal 12411 is covered by the upper cover 12412. Moreover, the upper cover 12412 has an opening (not shown). A first end of the push element 1242 is penetrated through the opening and contacted with the keycap 121. A second end of the push element 1242 is disposed within the casing 1241 and connected with the linkage element 1243. The linkage element 1243 is located at a middle region of the pedestal 12411. Moreover, the linkage element 1243 is movable upwardly or downwardly relative to the pedestal 12411. The linkage element 1243 has a protrusion structure 12431. The protrusion structure 12431 is extended from a sidewall of the linkage element 1243 toward the first spring strip 1244. The elastic element 1246 is located under the linkage element 1243. A first end of the elastic element 1246 is connected with the linkage element 1243. A second end of the elastic element 1246 is fixed on the pedestal 12411. Moreover, the elastic element 1246 provides an elastic force to the linkage element 1243.
The first spring strip 1244 is located near a sidewall of the pedestal 12411. The first spring strip 1244 comprises a first electric connection part 12441, an elastic part 12442 and a first fixing part 12443. The first fixing part 12443 is fixed on the pedestal 12411. Moreover, the first fixing part 12443 is arranged between the first electric connection part 12441 and the elastic part 12442. The elastic part 12442 is disposed within the casing 1241 and contacted with the protrusion structure 12431 of the linkage element 1243. Moreover, the elastic part 12442 can be swung relative to the first fixing part 12443. After the first electric connection part 12441 is penetrated downwardly through the pedestal 12411, the first electric connection part 12441 is contacted and electrically connected with the circuit board 11. The second spring strip 1245 is arranged between the linkage element 1243 and the first spring strip 1244. The second spring strip 1245 comprises a second electric connection part 12451, a conduction part 12452 and a second fixing part 12453. The second fixing part 12453 is fixed on the pedestal 12411. Moreover, the second fixing part 12453 is arranged between the second electric connection part 12451 and the conduction part 12452. The conduction part 12452 is disposed within the casing 1241. After the second electric connection part 12451 is penetrated downwardly through the pedestal 12411, the second electric connection part 12451 is contacted and electrically connected with the circuit board 11.
While the keycap 121 is depressed, the keycap 121 is moved downwardly to push the push element 1242. Since the linkage element 1243 is connected with the push element 1242, the linkage element 1243 is moved downwardly with the push element 1242. At the same time, the elastic element 1246 is compressed to generate the elastic force. As the linkage element 1243 is moved downwardly, the protrusion structure 12431 of the linkage element 1243 is contacted with the elastic part 12442 of the first spring strip 1244. Moreover, the protrusion structure 12431 is moved downwardly relative to the elastic part 12442 so as to push the elastic part 12442. Consequently, the elastic part 12442 is swung relative to the first fixing part 12443. As the linkage element 1243 is continuously moved downwardly, the swung elastic part 12442 correspondingly contacts and collides with the conduction part 12452 of the second spring strip 1245. Meanwhile, as shown in FIG. 2, the first spring strip 1244 and the second spring strip 1245 are in contact with each other. Consequently, the circuit board 11 generates a corresponding key signal. When the elastic part 12442 of the first spring strip 1244 collides with the conduction part 12452 of the second spring strip 1245, a click sound is generated. Due to the click sound, the user can feel the feedback of depressing the keycap 121. Moreover, when the keycap 121 is no longer depressed, the linkage element 1243 and the push element 1242 are moved upwardly in response to the elastic force of the elastic element 1246. Consequently, the keycap 121 is returned to its original position as shown in FIG. 1.
However, the key structure 12 of the conventional mechanical keyboard device 1 still has some drawbacks. For example, the contact area between the keycap 121 and the push element 1242 is too small. Consequently, the keycap 121 cannot be uniformly supported by the push element 1242. Since the keycap 121 is rocked and unstable in the forward/backward direction or the leftward/rightward direction, the tactile feel of operating the keycap 121 is deteriorated. Especially when the edge of the keycap 121 is depressed, the rocking extent of the keycap 121 becomes serious. In other words, the keyboard device and the key structure need to be further improved.